By default, a board is labeled with layer 25 (tName). I would also like to have layer 27 (tValue) printed on the board. What do I have to do when ordering?
Hi there 
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One way is to include the layer in a custom Gerber Output which you can generate using EAGLE, we provide a how-to for that: Exporting a custom Gerber file from EAGLE, please note that we do not support E-Testing or Assembly for this format.
If you have access to Fusion360, we recommend importing your design and create a custom ODB++ Output which supports E-Testing and Assembly.